Source : Webster's Revised Unabridged Dictionary (1913)

Water dropwort \Wa"ter drop"wort`\ (Bot.)
   A European poisonous umbelliferous plant ({Enanthe
   fistulosa}) with large hollow stems and finely divided
   leaves.

Source : WordNet®

water dropwort
     n : European poisonous herb having tuberous roots, yellow juice
         that stains the skin, yellow flowers and foliage
         resembling celery; all parts extremely poisonous [syn: {hemlock
         water dropwort}, {Oenanthe crocata}]